WASHINGTON --- Even if the mainstream U.S. media has been late in coming to the story, the largest defense program in U.S. history is facing two critical events this coming week.

As major British media has been reporting for some time, the F-35 Joint Strike Fighter may be facing a major international marketing embarrassment: It has failed to show up for two of three scheduled (and much ballyhooed) public demonstrations in the United Kingdom. Now, it may miss the main event, a flying demonstration before the world’s aviation community at the Farnborough International Airshow, starting Monday.

You see, the F-35 is grounded—again. An engine blew up on take-off at Eglin Air Force Base on June 23 and reportedly burned up much of the plane’s flammable, plastic composite rear fuselage and tail. No F-35s are flying until inspectors know what the problem is and can say it’s safe to fly—at least in the very limited regimes the F-35 has been cleared for. Moreover, even if the F-35 is released to participate at Farnborough, there may be a new problem: weather predictions for next week in England are not good, and the F-35 has real issues flying near thunder- and rainstorms; it even has problems with wet runways.

Stuck at home or coddled in UK hangars, the timing could not be worse for F-35 advocates. This Tuesday, the Defense Subcommittee of the Senate Appropriations Committee (SAC-D) will mark up its 2015 Defense Appropriations bill, and more than the usual routine approval of the Pentagon’s F-35 budget request is at stake. As pointed out in two timely commentaries (one by the Center for International Policy’s William Hartung and a second by Taxpayers for Common Sense’s Ryan Alexander), the House Appropriations Committee larded onto the already gigantic $8.3 billion request by adding four unrequested F-35s, costing an extra $479 million.

The four added planes are clearly at risk given the F-35’s self-embarrassment at Eglin, surely inspiring the F-35 talking points Lockheed is planting on the Members of the SAC-D well beyond their usual spinmeister fantasies on cost and performance. Worse, there could—at least theoretically—arise a critic of the F-35 in the membership of the SAC-D who might try to take real action on the F-35, beyond the rhetorical hyperbole that critics like Senator John McCain (R-AZ) have been hurling at the F-35. Imagine the shock and awe if some Member were to offer a meaningful amendment requiring the F-35 to be tested—actually imposing “fly-before-buy”—before a few hundred more mistake-laden jets are produced.

Not to worry: the F-35 defenders are rushing to the rescue. Beyond whatever election year financing promises major F-35 contractors Lockheed-Martin, Northrop-Grumman, and Pratt & Whitney may be distributing to keep the program on track, Secretary of Defense Chuck Hagel has just completed a baby-kissing exercise for the airplane. Travelling to Eglin Air Force Base where that F-35 destroyed itself, Hagel declared “This aircraft is the future of fighter aircraft for all our services,” thereby removing any notions that his junket might have some useful purpose other than showing fealty to the beleaguered F-35 program. Any expectation that he went to Eglin to exercise oversight of the F-35’s recurring embarrassments, as one might expect from a functioning Secretary of Defense, has been thoroughly excised. That leaves it up to the Defense Subcommittee of the Senate Appropriations Committee.

The SAC-D has many important defense spending decisions to make. None will be a better test of whether the committee is willing to conform DOD program ambitions to Pentagon budget realities than this point in the endless F-35 drama. Of course, the easy road beckons; defense business-as-usual will be happy to shower the Members with handsome signs of approval, material and otherwise.

Unfortunately, more of the same simply accelerates the decay of our defenses at ever-higher expense.

All eyes are turning to the Senate Appropriations Committee’s Defense Subcommittee. Thus far, political support for the F-35 has rolled over every ground truth, but realities like multiple groundings occurring amidst a continuing torrent of technical failures and cost overruns have a relentlessness all their own. Perhaps the only real question is when, not if, the politicians in Congress and the Pentagon will succumb to the inevitable tide. If next week does not end up as a tipping point for the F-35, it will come. It will come. And, that will be long before we buy the 2,433 Lockheed and its other boosters dream of.

Winslow Wheeler is Director of the Straus Military Reform Project, CDI at the Project On Government Oversight, POGO